pact_consumer: `each_like!` and nested structs

The PR #18 contains an each_like! macro which mimics Ruby's ArrayLike matcher. This generates a #{path}[*].* rule:

      def handle_array_like array_like, path, match_type
        record_rule "#{path}", 'min' => array_like.min
        record_match_type_rule "#{path}[*].*", 'type'
        recurse array_like.contents, "#{path}[*]", :array_like
      end

@bethesque argues that the #{path}[*].* rule is unnecessary.

We could remove that rule from Rust, but then we'd want to add a fields_like! macro so that you could write:

// This is an incredibly common Rust use case when generating JSON from domain objects.
each_like!(fields_like!(strip_null_fields(json!(DomainObject::factory()))

The each_like! would generate "#{path}" => { "matches": "type" }, and the fields_like! would generate the "#{path}[*].*" => { "matches": "type" } that each_like! generates now. Maybe fields_like! should also include a build-in strip_null_fields?

This is trivial to implement; so it's purely a design question. What do people think?

Review PR #18 and Bethesque's linked comment first, then compare the proposed each_like! and fields_like! macro semantics for nested structs and generated JSON rules. Done means reaching and documenting a decision on whether to remove the wildcard rule, add fields_like!, and include strip_null_fields; the issue does not name implementation files or tests.